Electrolytic device



Aug. 4, 1931. H. 0. slEGMUND 1,816,875

ELEcTRoLYnc DEVICE Fiied April 27, 1927v Patented Aug. 4, 1931 UNITED STAT-Es,

PATENT OFFICE HUMPHREYS O. SIEGMUND, OF WEST ORANGE, NEW JERSEY, ASSIGNOR IO WESTERN ELECTRIC COMPANY,Y INCORPORATED, OF- NEW YORK, N. Y., A CORPORATION OF NEW YORK ELECTROLYTIC DEVICE Application filed April 27,

This invention relates to electrolyticdevices, such -as electrolytic condensers,` and particularly to film forming electrodes thereor. v

In manufacturing electrolytic condensers and other electrolytic devices, it has been the practice to employ 'aluminum of a very high degree of purity as a material for the film forming electrode or anode. This practice is followed chiefly for the reason that the p presence of impurities in the aluminum tends to impair the film forming properties of the anode. For instance, the leakage resistance of the dielectric film of a condenser, the aluminum anode of which contains small amounts of other substances, such as `those listed below, is considerably lower than that of a condenser the film forming electrode of which is of substantially `pure aluminum. When the other substances contained in the film forming elect-rode are greater than 2% or 3%, the film forming properties of the electrode are so greatly impaired that its use is unsuitable even in apparatus designed for use with low voltages. When employing electrodes of substantially pure aluminum in electrolytic devices, the useful life of the device has been found in many cases to be very short due to the corrosion of the electrodes.

In accordance with the present invention there is provided for an electrolytic device a film forming electrode comprising mainly a film forming metal, such as aluminum, ytogether with other materials, which may or may not be film forming, in such amounts that the ability of the electrode to resist corrosion is considerably increased. An electrode comprising between 98.0% and 99.2i% aluminum and the rest other metals, such as those mentioned below, combined therewith, is characterized by a high resistance to corrosion as compared with the corrosion-resisting properties of an electrode formed ofsubstantially pure aluminum and the film forming properties of such an electrode have been found to be satisfactory. If the film forming properties of the material are not thereby impaired, lower percentages of aluminum 1927. Serial No. 187,068.

may be employed. For instance, two or more film forming materials such as magnesium and aluminumf may be combined in various proportions. In a preferred embodiment of the invention the following metals were combined with the pure aluminum in the amounts stated: Silicon 0.3%; manganese 0.05%; iron 0.30%.

The accompanying drawing shows an electrolytic condenser in which this invention has an embodiment. The condenser comprises a jar l for containing an electrolyte 2 in which an anode or film forming electrode 3 and a cathode 4 are positioned. While various electrolytes may be employedone which aiforded satisfactory results was prepared from 450 grams boric acid, 75 c.c. ammonium hydroxide and 5 gallons distilled water. The cathode 4 -is preferably non-film -forming and may comprise aluminum together with sufficient other materials to render it substantially non-film forming as disclosed in Patent No. 1,578,857 of I-I. O. Siegmund et al, March 30, 1926. rI"he anode 3 is composed chiefly of aluminum together withother materials in amounts which-are insufficient to render the anode non-film forming. An anode comprising aluminum together with these materials is characterized by its increased ability to resist corrosion due to the action of the electrolyte, as compared with the corrosion-resisting properties of substantially pure aluminum. It has been found that a condenser employing an anode which comprises approximately 99.6%. aluminum fails to function satisfactorily after a period of 3 or 4 months. While it has not as yet been determined just what the life of an electrolytic device will be when employing an anode composed of aluminum, with a low percentage of alloying materials, the results of tests made thus far indicate that it will be of the order of 6 or 7 years.

The following table shows the results of tests made on electrolytic condensers employing electrodes ,of aluminum with various amounts 'of other substances. These electrodes were immersed in an electrolyte of ammonium borate for a period of more than 12` months and the percentage of failures noted:

Per cent of Total Fail- Man- Cop- Aluures Smm ganese non per bon rir minum None o. 23' 0.07 o. 64 n. 08 .04 1. o6 9s. 94 2. 36 0. 04 0. 36 Trac NODE 76 99. 24 13. 6 0. 40 0. 0l v 49 Tlae 0. 03. 0. 93 99. 07 30. 0 0. 13 N011@ O. 28 NOUS 0. 04 0. 45 99. 55 39. 0 0. 05 03 0. 50 08 0. 04 0. 70 99. 30

While these tests do not afford suiiicient data from which to determine with accuracy the amount and kind of materials which can b e contained in the the aluminum anode in order to obtain minimum corrosion together with satisfactory film. forming properties, they do indicate that an anode comprising between 98.0% and 99.4%' aluminum will give satisfactory results. The alloying ma.- terials combined with, the aluminum should preferably comprise one'or more of the following: Silicon 0.2% to 1.5%; maganese 0.04% to 1.50%; iron 0.3% to 14.5%. Of these, it is believedA thatl silicon is themost l important.

' trolytic device comprising mainly pure alu- The dielectric ilm formedA on the a-nodes of all of the condensers used in these tests Was satisfactory initially. After the dielectric ilm was formed by applying a gradually increasing potential across the electrodes Aof the condenser, the leakage current at 40 volts.

was found tobe less than .035 amperes. The capacity of each of the condensers was about .001 farad and the resistance of each at cycles was less than 1 ohm.

, What is claimed is:

1. A film forming electrode tornan electrolytic device comprising a film orming metal containing 'aluminum and having a small percentage of a substantially non-film forming metal combined therewith for improving the corrosion-resisting properties-oi` the electrode, said metal comprising silicon, manganese and iron.

2. A ilm forming electrode for an elecaluminum and approximately .25% silicon.

5. A film forming electrode for an elec-y minum, small quantities of silicon and iron, and between 0.04% and 1.5% manganese.

6. A ilm forming electrode for an electrolytic device comprising mainly pure aluminum, small quantities of silicon and manganese, and between 0.3% and 1.5% iron.

7. A film forming electrode for an elecl trolytic device comprising between 98.0%

and 99.4% pure aluminum, a small quantity of manganese and approximately .25% silicon..

8. A ilm forming electrode for an electrolytic device comprising between 98.0%

and 99.4% pure aluminum, small quantities of silicon and iron, and approximately .05% manganese.

9. A film forming electrode for an elec-v trolytic device comprising mainly pure aluminum, together with a small amount of manganese, and approximately 0.3% iron and 0.3% silicon.

10. A lilm forming electrode for an electrolytic device comprising mainly pure aluminum, together with a small amount of iron, and approximately 0.3% silicon and 0.05%.manganese- 11. A film forming electrode for an electrolytic device comprising mainly aluminum, together with approximately 0.3% silicon, 0.05% manganese and 0.3% iron.

vIn witness whereof, I hereunto subscribe my name this 27th day of April, A. 13.1927.

HUMPHREYS O. SIEGMUND. 

